David Aviles, Ian Ebert and Lauren Tombari all ask (to quote Mr Aviles), "If [Indians] had such a large population, why hadn't they developed as much as other countries?" The answer to this very important question is complicated, but part of it surely is that evaluating relative levels of technological development is not so easy, and that it isn't at all clear that native peoples were less developed in this area than Europeans or Asians. As the historian Alfred Crosby has repeatedly observed, societies tend to measure "progress" in terms of things that they are good at. Europeans were good at making metal tools and devices, so we tend to look for them -- Indians didn't have steel axes and geared machines, so they must be inferior. But many Indian societies were extremely deft about agriculture. Looking at a Europe afflicted by recurrent famine, one can imagine them viewing these societies as so undeveloped that they were unable to feed themselves. It's hard to say which view is correct.
And there you have it. This, of course, meshes nicely with the point that Europeans didn't so much defeat the native population with superior war-making abilities as they did simply take advantage of massive levels of epidemic disease which killed off most of their foes.